Photocathode Quantum Efficiency of Ultra-Thin Cs2Te Layers On Nb Substrates

The quantum efficiencies (QE) of photocathodes consisting of bulk Nb substrates coated with thin films of Cs2Te are reported. Using the standard recipe for Cs2Te deposition developed for Mo substrates (220 {\AA} Te thickness), a QE ~11% - 13% at light wavelength of 248 nm is achieved for the Nb substrates, consistent with that found on Mo. Systematic reduction of the Te thickness for both Mo and Nb substrates reveals a surprisingly high residual QE ~ 6% for a Te layer as thin as 15 {\AA}. A phenomenological model based on the Spicer 3-Step model along with a solution of the Fresnel equations for reflectance, R, leads to a reasonable fit of the thickness dependence of QE and suggests that layers thinner than 15 {\AA} may still have a relatively high QE. Preliminary investigation suggests an increased operational lifetime as well. Such an ultra-thin, semiconducting Cs2Te layer may be expected to produce minimal ohmic losses for RF frequencies ~ 1 GHz. The result thus opens the door to the potential development of a Nb (or Nb3Sn) superconducting photocathode with relatively high QE and minimal RF impedance to be used in a superconducting radiofrequency (SRF) photoinjector.Comment: 12 pages, 3 figure

Modeling Study of the Dip-Hump Feature in Bi₂ Sr₂ CaCu₂ O\u3csub\u3e8+δ\u3c/sub\u3e Tunneling Spectroscopy

The tunneling spectra of high-temperature superconductors on Bi2 Sr2 CaCu2 O8+δ (Bi-2212) reproducibly show a high-bias structure in the form of a dip-hump at voltages higher than the gap voltage. Of central concern is whether this feature originates from the normal state background or is intrinsic to the superconducting mechanism. We address this issue by generating a set of model conductance curves-a normal state conductance that takes into account effects such as the band structure and a possible pseudogap, and a pure superconducting state conductance. When combined, the result shows that the dip-hump feature present in the experimental conductance curves cannot be naively attributed to a normal state effect. In particular, strong dip features found in superconductor-insulator-superconductor data on optimally doped Bi-2212, including negative dI /dV, cannot be a consequence of an extrinsic pseudogap. However, such features can easily arise from state-conserving deviations in the superconducting density of states, e.g., from strong-coupling effects

A Study of Mosque Mimbar Entrance

One of the mosque component or elements is mimbar. Mimbar is a place where khatib giving khutbah or speech. This research is about a study of mosque mimbar entrance. The aim of study is to identify mosque mimbar entrance typology. This study through observation of Mosque mimbar around Kota Setar district. Data collected by taking photograph and site visit. As a result, based on data collected shows that there are several type of mosque mimbar entrance which is entrance from front, side and from back. Most of the mosque mimbar entrance is from the front which is facing qiblat

A Study of Mosque Water Consumption using Self Closing Tap

Water is important resource used in the mosque for many activities such as for ablution, cleaning, landscape watering and toilet. There are many types of tap use for ablution. One of it is self-closing tap. This research is a study to identify mosque water consumption using self-closing tap in Masjid Assiddiq, Seri Iskandar, Perak. This study carried through observation and site visit. The data of water consumption identified by reading water meter daily basis. Water consumption shows decrease and save about RM15 per month by using self-closing tap

Tunneling Spectroscopy of Tl2Ba2CuO6

New results from tunneling spectroscopies on near optimally-doped single crystals of Tl_{2}Ba_{2}CuO_{6} (Tl-2201) junctions are presented. The superconductor-insulator-normal metal (SIN) tunnel junctions are obtained using the point-contact technique with a Au tip. The tunneling conductances reproducibly show a sharp cusp-like subgap, prominent quasiparticle peaks with a consistent asymmetry, and weakly decreasing backgrounds. A rigorous analysis of the SIN tunneling data is performed using two different models for the $d_{x^{2}-y^{2}}$ (d-wave) density of states (DOS). Based on these and earlier results, the tunneling DOS of Tl-2201 have exhibited the most reproducible data that are consistent with a d-wave gap symmetry. We show that the dip feature at $2\Delta$ that is clearly seen in SIN tunneling data of Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} is also present in Tl-2201, but at a weaker level. The gap values for crystals with a bulk T_c = 86 K are in the range of 19-25 meV.Comment: 7 pages, 5 figure

Kelvin Probe Studies of Cesium Telluride Photocathode for AWA Photoinjector

Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (~50 nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.Comment: 5 pages, 6 figure

Urban competitiveness vis-a-vis sustainable urban development: A discourse on urban development in Malaysia

With the advent of economic globalization, sustainable urban development efforts are facing a new challenge whereby cities must not only be seen as sustainable and livable but also competitive enough in attracting foreign direct investments. As such, local authorities now find themselves struggling to achieve sustainable urban development objectives while at the same time under great pressure to create favourable climates for economic investment particularly in the manufacturing and service sectors. The two sustainability and competitiveness concepts may not be entirely compatible but they are organically interrelated. This article discusses both concepts, highlights their differences and similarities, and addresses some of the common elements which could be applied in the field of urban management. The paper concludes that although the relationships between urban sustainability and urban competitiveness are not entirely adversarial, fundamental incongruities in objectives and impacts remain. These have the potentials of generating conflicts in the course of urban management not least because they were motivated by different values. What is needed then is a more pragmatic approach that could reconcile the divergent objectives, a challenge that only amplifies the importance of the synthesising role of local authoritie

Optimization of Transmission Mode Metallic (Aluminum) Photocathodes

AbstractTransmission mode metallic photocathodes are studied, especially for aluminum ones, to test complete 8“x8” largearea planar photodetectors in ambient condition. We have derived a quantitative model for transmission mode metallic photocathodes which permits optimization of the thickness of these cathodes (approximately 15∼20 nm) and estimation of quantum efficiency based on the theory and the known parameters from the literatures

Simultaneous quasiparticle and Josephson tunneling in BSCCO-2212 break junctions

Tunneling measurements are reported for superconductor-insulator-superconductor (SIS) break junctions on underdoped, optimally-doped, and overdoped single crystals of tSrsCaCiOs-).,! (Bi2212). The junction I -V characteristics exhibit welldefined quasiparticle current jumps at eV = 2A as well as hysteretic Josephson currents. The quasiparticle branch has been analyzed in the framework of dxa_y2 (d-wave) superconductivity and indicates that there is preferential tunneling along the lobe directions of the d-wave gap. For overdoped Bi-2212 with TC-62 K, the Josephson current is measured as a function of junction resistance, Rn, which varied by two orders of magnitude (1 kO to 100 kO). IcRn product is proportional to the 0.47 power of /c and displays a maximum of 7.0 mV. When the hole doping is decreased from overdoped (Tc=62 K) to the underdoped regime (Tc=70 K), the average IcRn product increases as does the quasiparticle gap. The maximum IcRn is ~ 40% of the A/e at each doping level, with a value as high as 25 mV in underdoped Bi-2212